Ran into a problem couple of days ago where a the contents of a div tag (used for a popup menu) was displaying behind a flash movie also on the same page. the are where the div overlaps with the flash movie gets cut off. playing with different values of z-index did not help.
Using ‘wmode’ parameter with the value ‘transparent’ for the <object> and <embed> tags worked perfectly.
<object ...> <param name="wmode" value="transparent"/> ... <embed ... wmode="transparent".../> </object>
(Found the solution at http://www.webmasterworld.com/css/3468404.htm; thx to the person ‘Achernar’ who gave the solution)